Ephemeron

Part of speech: noun

Definitions

1. A fleeting organism or momentary phenomenon that exists or matters only briefly before vanishing entirely
2. An object or entity that endures for a very brief time, disappearing almost immediately after coming into existence
3. Refers to something whose presence or impact is extremely temporary, vanishing soon after it appears

Etymology: Aristotle reported a creature on the river Hypanis, near the Cimmerian Bosporus, that lived for a single day. Small sacs drifted down the water around the summer solstice, he wrote, and out of them broke a winged, four-footed creature that flew from morning until evening and died as the sun went down. The Greeks called it "ephemeron," and that is the word English later borrowed. "Ephemeron" is the neuter form of the adjective "ephemeros," built from "epi" (on) and "hemera" (day), so it meant something that exists only for a day. A century before Aristotle, the Greeks had already turned the adjective on themselves. In his eighth Pythian ode Pindar called human beings "creatures of a day": "What is someone? What is no one? Man is the dream of a shadow." Physicians carried the root into Latin and then into English. A fever that rose and broke within a day was an "ephemera," and "ephemeral" first entered English in the sixteenth century as a medical term for such brief illnesses. The Greek noun itself came into English through natural history, where it named Aristotle's day-insect, which was soon identified with the mayfly. The identification was apt. Adult mayflies cannot feed, and some species live only hours after leaving the water. Linnaeus gave their genus the name Ephemera, and entomologists of the late nineteenth century built the order name Ephemeroptera, "day-wings," from the same Greek roots. From the insect the noun spread to anything fleeting. Its Greek plural, "ephemera," took on a life of its own as the name for paper never meant to last: tickets, handbills, menus and posters, which collectors and archives now preserve with great care. The word's latest life is in computing. In 1997 the computer scientist Barry Hayes gave the name "ephemeron" to a key–value pair whose value the memory manager keeps only as long as the key is still reachable from elsewhere in the program. Once the key is forgotten, the pair vanishes too, a thing whose whole existence hangs on something else, as briefly as Aristotle's insect.

Synonyms: transient, momentary, fugitive, temporary, impermanent

Antonyms: permanent, everlasting, enduring, lasting, constant